Conveyance systems, i.e., systems for conveying articles, are used in various applications, such as in a production unit in a factory. Articles that are conveyed in a conveyance system are hereinafter referred to as “workpieces.” A conveyance system usually includes an actuator for moving workpieces, a sensor for detecting workpieces, and a controller for controlling the actuator and the sensor. Simulation techniques have conventionally been used for the performance test of the controller.
Japanese Patent Application Laid-Open No. 2014-148389 (Patent Literature 1) discloses an information processor that performs a simulation operation of conveying carrier articles by a conveyor. A workpiece, a lifter, and a table are disposed in a three-dimensional simulation space. The information processor executes a simulation operation of conveying the workpiece disposed on the table by the lifter. When the lifter moves the workpiece on the table in an upward direction, the information processor sets a priority that indicates the degree of integration of the lifter with the workpiece to be higher than a priority that indicates the degree of integration of the table with the workpiece. When the lifter moves to below the table during conveyance of the workpiece, the information processor sets the priority of the lifter to be lower than the priority of the table.
Japanese Patent Application Laid-Open No. 2014-063327 (Patent Literature 2) discloses a simulation device. The simulation device includes a processor that performs a simulation of a control program that is executed by a controller for controlling the movement of a machine that handles target articles. The processor includes operation control means, determination means, and follow-up means. The operation control means controls the movement of a virtual machine, which corresponds a machine in a virtual space, according to the control program and on the basis of an operation command to move the virtual machine. The determination means determines, on the basis of model data of a virtual target article that corresponds to a target article handled by the virtual machine and model data of the virtual machine, whether the volume of the region where the virtual target article overlaps with a working space in which the virtual machine can operate is greater than or equal to a predetermined reference value. When the volume is greater than or equal to the reference value, the follow-up means causes the virtual target article to follow the movement of the virtual machine based on the operation command.
Japanese Patent Application Laid-Open No. 2002-358114 (Patent Literature 3) discloses a simulation device that performs a simulation of operations of equipment in accordance with a program for a sequencer. The simulation device includes state calculation means and pseudo-signal generation means. The state calculation means simulates a change in the state of the equipment on the basis of an output from the sequencer and calculates a state of change in the equipment at a predetermined time interval. The pseudo-signal generation means generates a pseudo signal in accordance with the state of change in the equipment calculated by the state calculation means, the pseudo signal being a signal to be output to the sequencer and relevant to the above state. That is, this simulation device performs a simulation in two steps. First, the simulation device simulates the output from the sequencer, i.e., how the state of the equipment changes in accordance with the operation command. Then, the simulation device simulates whether the equipment has entered a state of generating the pseudo signal, or in short, whether there is a change in the output of a detector that detects a change in the state of the equipment, as a result of the movement of the equipment. The state of the equipment as used herein refers to, for example, the state of the actuator and the workpiece. The detector may be configured to detect whether the workpiece is present at a predetermined position.
Japanese Patent Application Laid-Open No. 2002-351511 (Patent Literature 4) discloses an input generation device for use in a controller. The controller includes PLC means, input interface means, and output interface means. The PLC means has functions defined as software and executes a control application. The input interface means interfaces signals from actual processes to the PLC means. The output interface means interfaces signals from the PLC means to actual processes. The input generation device applied to the controller includes pseudo-input generation means having functions defined as software, and actual input-pseudo input switching means. The pseudo-input generation means generates a simulated input signal in accordance with a signal from the output interface means. When using the simulated input signal, the actual input-pseudo input switching means supplies the signal received from the output interface means to the pseudo-input generation means and supplies an output signal of the pseudo-input generation means to the aforementioned input interface means.